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The spatial pattern of plant communities can be an indicator of the processes that regulate community structure and their interplay with environmental drivers such as climate. However, to exploit such indicators we need a fuller understanding of the links between spatial pattern and climate. We examined variation in spatial pattern of annuals/biennials and perennials in a range margin steppic plant community in Germany over 26 years. We assessed change in spatial pattern through time, and how this change was related to local variation in climate and community composition. We found increasing dissociation between annuals/biennials and perennials through time, and a response of spatial pattern to summer temperature and precipitation. These responses are associated with the occurrence of Centaurea stoebe, a species which establishes in the community mid-way through the recording period. Our results indicate that in some circumstances spatial patterning of vegetation may not be directly linked to environmental severity, and that species turnover rather than changes in the interactions or abundance of species already in the community can influence the observed dynamics of vegetation spatial pattern. Thus, they support calls for a better understanding of the context-specificity of plant–plant interactions, their translation to spatial pattern, and their regulation by climate and other drivers such as species turnover.

Plants with larger and longer-lived flowers receive more pollinator visits and increase reproductive success, though may also suffer more from antagonistic interactions with animals. Florivores can reduce fruit and seed production, so selection on flower size, floral longevity and/or number of flowers may thus be determined by the relative effects of both pollinators and florivores. In this study flowers of Cistus ladanifer, a large-flowered Mediterranean shrub, were monitored to evaluate the effects of flower size, floral longevity and number of flowers on levels of florivory in four populations. Number of flowers was variable but did not differ among populations. Both flower size and floral longevity of C. ladanifer showed broad variation and significantly differed among populations. Overall, 7% of flowers suffered attack by florivores, which were mainly ants picking the stamens and beetles consuming petals and pollen. Within-populations, larger and longer-lived flowers tended to be affected by florivores more frequently. The low overall incidence of florivores and its lack of between-population variation suggest that florivory may not influence intraspecific variation of these floral traits. However, moderate florivory levels on the largest and longest-lived flowers open the possibility of exerting selection towards smaller and shorter-lived flowers in some of the populations studied.

The high self-shading found in Quercus suber seedlings has been interpreted as a feature common for plants growing in high light environments. But many studies reveal that Q. suber has high survival rates under low-light conditions, so a high degree of self-shading could be the consequence of a foliage composed of many small leaves, with no drawbacks for coping with low light. A characterization of the light environment in a Q. suber stand together with a study of photosynthetic parameters of full sunlight-exposed (FSLE) and self-shaded (SS) leaves were carried out to tackle this apparent contradiction. Although the number of sunflecks longer than 120 min during the 3 months of measurements was low, the occurrence of at least one sunfleck longer than 120 min per day in the understory of the forest studied was very common. Sunflecks shorter than 30 min promoted an increase in net photosynthesis ( A ) in FSLE leaves, but not in SS leaves. However, sunflecks longer than 60 min led to a very strong decrease in A and in actual photosystem II efficiency (Φ PSII ) in FSLE leaves, when compared to sunflecks shorter than 30 min. In SS leaves, changes were, again, negligible. The multi-layered foliage of Q. suber seedlings allowed i) FSLE leaves to obtain the maximum photosynthetic yield for short sunflecks, and ii) SS leaves to increase their contribution to the photosynthesis of the whole plant for long sunflecks, thus, optimizing the use of light by FSLE and SS leaves during short and long sunflecks respectively. Therefore, shoot architecture of Q. suber seedlings involving high levels of self-shading allows to adequately cope with the low but highly heterogeneous light conditions of the understory, particularly when sunflecks of contrasting durations take place as it is frequently the case for evergreen Mediterranean forests.

Grassland plant species have traditionally been classified into two groups, increasers and decreasers, based on changes in their relative abundance in the presence or absence of grazing. However, the ecophysiological mechanisms underlying these opposing strategies remain unclear. Seeds of ten Mediterranean species of known grazing status were germinated in different light environments to test the hypothesis that grazing selects light-dependent germination amongst grazing increasers. Two light quantity levels (Photosynthetical Active Radiation, PAR) and five light quality levels (red:far-red ratio, R:FR) were used to quantify percentages of germination of viable seeds and number of days elapsed to reach 50% of germination (T50), measured using five replicates of each light treatment and species combination. There were no differences in response to light quantity between the two grazing status groups; germination was inhibited in both groups at higher light intensities. However, increasers had lower germination percentages at low R:FR ratios, while decreasers were not affected by light quality. Germination speed (T50) was affected differently by light quality in each grazing status. There was an increase in germination speed at the lowest R:FR ratio only in increaser seeds, whereas decreaser germination speed was not affected by the treatment. PAR affected T50, regardless of grazing status; germination was faster at lower light intensities. Increaser seeds germinated faster than decreasers. These results reveal that the differential control of germination by light quality is a key factor in determining the species composition of grassland plant communities affected by herbivores in semi-arid Mediterranean grasslands.

Plant transpiration has a key role on both plant performance and ecosystem functioning in arid zones, but realistic estimates at appropriate spatial-temporal scales are scarce. Leaf and tiller morphology and crown architecture were studied together with leaf physiology and whole plant water balance in four individual plants of Stipa tenacissima of different sizes to determine the relative influence of processes taking place at different spatial and temporal scales on whole plant transpiration. Transpiration was estimated in potted plants by leaf-level gas exchange techniques (infrared gas analyzer and porometer), by sap flow measurements, and by integrating leaf physiology and crown architecture with the 3-D computer model Yplant. Daily transpiration of each individual plant was monitored using a gravimetric method, which rendered the reference values. Leaves on each individual plant significantly varied in their physiological status. Young and green parts of the leaves showed five times higher chlorophyll concentration and greater photosynthetic capacity than the senescent parts of the foliage. Instantaneous leaf-level transpiration measurements should not be used to estimate plant transpiration, owing to the fact that extrapolations overestimated individual transpiration by more than 100%. Considering leaf age effects and scaling the estimates according to the relative amount of each foliage category reduced this difference to 46% though it was still significantly higher than gravimetric measurements. Sap flow calculations also overestimated tussock transpiration. However, 3-D reconstruction of plants with Yplant and transpiration estimates, considering both the physiological status and the daily pattern of radiation experienced by each individual leaf section within the crown, matched the gravimetric measurements (differences were only 4.4%). The complex interplay of leaf physiology and crown structure must be taken into account in scaling up plant transpiration from instantaneous, leaf-level measurements, and our study indicates that transpiration of complex crowns is easily overestimated.

Inter-specific differences in seedling survival responses along a sun-shade gradient and the influence of low-water availability were examined for four Iberian tree species (Q uercus robur L., Quercus pyrenaica Willd., Pinus sylvestris L. and Pinus pinaster Ait.) typical of the cool temperate–Mediterranean transition zone. Seedlings were grown under controlled conditions in a factorial experiment with four levels of irradiance (1%, 6%, 20% and 100% of full sunlight) and two levels of water availability. Five censuses (from late spring to autumn) leading to four regular intervals (T 0 → T I ; T I → T II ; T II → T III ; T III → T IV ) were established. Statistical models of seedling survival as a function of irradiance were calibrated throughout the whole experiment (T 0 → T IV ) and also for each time interval and water availability level. Seedling survival responses among different species diverged both in the type of functional response to irradiance and in their response to water stress. Ranking of species according to shade tolerance ( Q. pyrenaica > Q. robur > P. sylvestris > P. pinaster ) contrasted with tolerance of high irradiance and conformed to a hypothetical sun-shade trade-off for survival (i.e. species having higher survival in low irradiance—oaks—had poorer survival at high irradiance and vice-versa). Low-water availability also differentially affected each species, with pines being more drought tolerant than oaks. At an intra-specific level, low-water availability decreased survival of Q. pyrenaica under both high and low irradiance. For Q. robur , however, low-water availability exerted a relatively stronger effect under low irradiance. Consequences of the interplay between irradiance and water availability for explaining segregation and coexistence of forest tree species at the ecotone between cool temperate and Mediterranean forests are discussed.